Significant amounts of alpha pyridine coenzymes should be present in vivo based on the anomeric equilibration between alpha NADH and beta NADH and the 20 mv more negative redox potential for the alpha coenzymes. The absence of significant levels of alpha coenzymes in vivo indicates probable metabolic regulation. This proposal is for the investigation of the in vivo formation, metabolism and fate of alpha pyridine coenzymes. Intramolecular interactions in the pyridine coenzymes are implicated in influencing their conformation, chemical reactivity an enzymic activity. Pyridine coenzyme analogs will be synthesized in which specific interactions are altered by modifications in the ribose or pyrophosphate moieties. Efforts are to be made to correlate the specific interactions with alterations in the chemical, physical and enzymic properties.